1. FIELD OF THE INVENTION
The present invention relates to a method of detecting contacting position in a touch panel sensor.
2. DESCRIPTION OF THE PRIOR ART
There have been widely used touch panel sensors which generate a signal representing two dimensional coordinate position by detecting a position of a panel depressed by means of a finger or pen. Since the touch panel formed by transparent members is attached to the surface of a display device, the touch panel is used as a simple picture data signal input device.
FIG. 1 shows an example of a conventional touch panel sensor 1 of a voltage dividing type using resistance layers.
Referring to FIG. 1, a pair of transparent insulation films 3, 3' of a generally rectangular shape, each having a transparent conducting layer 2, 2' of a rectangular shape with a predetermined surface resistance (referred to as a resistance layer 2, 2' hereinafter) formed on one surface of the film 3 (3') are so disposed and separated with a predetermined gap by a plurality of dot spacers 4 projected from on insulation film that the respective resistance layers 2 and 2' face each other.
Two conduction lines 5a and 5b are formed on the surface of the insulation film 3 so that the conduction lines 5a and 5b are electrically connected to opposite edges of the resistance layer 2. The conduction lines 5a and 5b are adapted to be applied with a DC voltage so that there is developed a potential gradient directed from the conduction line 5a to 5b. It is noted that the direction from the conduction line 5a and 5b is designated as the X direction. Similarly, two conduction lines 5a' and 5b' are formed on the surface of the insulation film 3' in such a manner that the conduction lines 5a' and 5b' are electrically connected to opposite edges of the resistance layer 2' so that another voltage gradient is developed on the resistance layer 2' in a Y direction which is perpendicular to the X direction of the voltage gradient developed on the resistance layer 2. 6a, 6b, 6 a' and 6b' denote connection lines formed on the insulation films 3 and 3' for the conduction lines 5a, 5b, 5a' and 5b'.
In the touch panel mentioned above, when a portion of the outer surface of the touch panel is depressed by finger or pen, the insulation film is deformed and a portion of the resistance layer 2 contacts with the resistance layer 2'. If the finger or pen is removed from the insulation film, the portion of the resistance layer 2 is separated from the resistance layer 2'.
The conventional method of detecting the coordinate position (x and y) at the contact position P in the touch panel will be explained hereinafter.
In the conventional touch panel, DC voltage is applied to the resistance layer 2 first through the conducting lines 5a and 5b, and subsequently the DC voltage is applied to the resistance layer 2' through the conduction lines 5a' and 5b'.
When the touch panel is depressed at the position P and DC voltage Vx is applied to the resistance layer 2 through the conduction lines 5a and 5b, since a voltage v.sub.x at the point P of the resistance layer 2 is applied to the point P of the resistance layer 2', the X coordinate position of the position P in the X direction can be known by detecting the voltage between the conduction lines 5a' and 5b' of the resistance layer 2'. Subsequently when the DC voltage Vy is applied to the resistance layer 2' through the conduction lines 5a' and 5b', a voltage v.sub.y on the position P of the resistance layer 2' is applied to the position P of the resistance layer 2, the position P in the Y direction can be known by the voltage on the conduction lines 5a and 5b.
As mentioned above, in the conventional method of detecting the contact position of the touch panel, the DC voltages must be switched alternately to the resistance layers 2 and 2'. In the practical use, the voltage detection for the respective resistance layers 2 and 2' must be made within short periods, and therefore, there must be provided a high speed switch for rapidly switching the voltage to the respective resistance layers 2 and 2'.
Therefore, the conventional method for detecting the contact position using a touch panel requires a complicated and expensive arrangement, and moreover, accidents tends to occur.